Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome. You may report side effects to FDA at 1-800-FDA-1088.

What is the most important information I should know about isoniazid ()?

Take all of the isoniazid that has been prescribed for you even if you begin to feel better. Your symptoms may begin to improve before the infection is completely treated.

Avoid alcohol while taking isoniazid. Alcohol may increase the risk of damage to the liver during isoniazid treatment.

Contact your doctor immediately if you experience numbness or tingling in the hands or feet, weakness, fatigue, loss of appetite, nausea and vomiting, yellowing of the skin or eyes, or darkening of the urine.